— A medication commonly used to treat post-traumatic stress disorder in combat veterans may not be effective in reducing overall PTSD severity, a new study shows.

The six-month randomized, controlled trial found that the antipsychotic medication risperidone worked no better than a placebo in alleviating typical PTSD symptoms in patients who had been suffering from the disorder long-term or who continued to suffer symptoms after being treated with antidepressants.

The medication also failed to quell depression and anxiety, researchers reported today in the Journal of the American Medical Association.

“PTSD is the most common — and most costly to treat — disorder seen by the VA psychiatry services,” said the study’s lead author, Dr. John H. Krystal, professor and chair of the department of psychiatry at Yale University and director of the clinical neuroscience division of the Veterans Administration National Center for PTSD. “It’s a huge problem.”

Standard treatments, including antidepressants like Zoloft and Paxil, help a lot of people with the disorder. But studies have suggested that these drugs don’t work so well for people who have had multiple traumas or chronic PTSD, Krystal said. So doctors have turned to alternative medications like risperidone to add to antidepressant therapies.

Risperidone is an antipsychotic medication used to treat mental illnesses such as schizophrenia, bipolar disorder and irritability associated with autism disorder. In 2009, nearly 87,000 veterans diagnosed with PTSD received an antipsychotic prescription, with nearly 94 percent of them for second-generation antipsychotics such as risperidone.

Krystal and others suspect that the new findings will affect the prescribing habits of doctors trying to help patients suffering from PTSD.

“So here we have the situation where one of the most commonly prescribed medications for the treatment of PTSD turns out not to be effective in reducing the overall severity of PTSD or improving other types of outcomes, such as quality of life,” Krystal said. “Which really gives you pause.”

The new study followed 247 veterans with military-related PTSD, half of whom received risperidone while the other half got placebos. If patients were already taking PTSD medications such as antidepressants, they continued to take these medications along with the risperidone.

At the end of the study, the researchers were surprised to see that risperidone was no more effective in reducing the severity of PTSD than placebos.

“We fully expected we would find it to be effective on the basis of preliminary studies that found risperidone effective and because it was so widely prescribed,” Krystal said. “But we found that it was not only not better than placebo at reducing overall symptoms, but also it was not better in reducing anxiety, depression, or in improving quality of life.”

The researchers also found that the medication was associated with side effects, such as weight gain, sleepiness, and drowsiness.

Drug did relieve nightmares, nervousnessRisperidone did provide a little relief for certain types of symptoms, Krystal said. “It was statistically effective in reducing symptoms such as nightmares, flashbacks, and daydreams that included intrusive thoughts about the trauma,” he explained. “It also helped with hyperarousal symptoms such as nervousness and jumpiness.

“But the size of the effect was very small and it wasn’t clear to us that these changes were really clinically significant. And they were not associated with other changes, like improvement in quality of life or overall clinical impression.”

Krystal cautioned that the study might not apply to all PTSD patients. That’s because the study did not include patients who suffered from high levels of psychosis as a result of their PTSD. Those patients might receive more benefit from risperidone, Krystal said.

Experts welcomed the new results, even if they were disappointed to see that the medication wasn’t effective.

“You need a study like this to show that the medication isn’t as effective as we had hoped,” said Dr. Steven Berkowitz, an associate professor of clinical psychiatry at the University of Pennsylvania and director of the Penn Center on Child and Family Trauma Response and Recovery.

Such studies may prompt more people to seek help from psychotherapy, Berkowitz said. While medications seem to offer a quick and easy answer, they can fall short when it comes to treating complex disorders like PTSD, he added.

“Often we try to find things that are effective but easy to use,” Berkowitz said. “But medications aren’t, by and large, as effective as psychotherapy and they come with a lot of side effects.”

The new study highlights the need for a wider range of treatments, said Dr. Ian Cook, the Miller professor of psychiatry at the University of California, Los Angeles.

“PTSD is a fairly common illness, affecting seven to eight million Americans,” Cook said. “The challenge is to try to help the many for whom first and second line treatments don’t work. About 30 percent of people with PTSD will develop a chronic form that goes on and on for years.”

Cook hopes that this study won’t discourage people from seeking help. “PTSD can be such a dangerous illness,” he explained. “People really need to get treatment. It can lead to suicide. It can lead to violence when someone is having a flashback. People need to get care.”